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412940 minor threadsafe fixes 

hold lock for accessing elements size
This commit is contained in:
Greg Wilkins 2013-07-15 17:00:51 +10:00
parent 8d49f69aa4
commit e758e0111b
1 changed files with 125 additions and 121 deletions
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246
jetty-util/src/main/java/org/eclipse/jetty/util/BlockingArrayQueue.java
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@ -34,29 +34,25 @@ import java.util.concurrent.locks.ReentrantLock;
/** /**
* A BlockingQueue backed by a circular array capable or growing. * A BlockingQueue backed by a circular array capable or growing.
* <p/> * <p/>
* This queue is uses a variant of the two lock queue algorithm to provide an * This queue is uses a variant of the two lock queue algorithm to provide an efficient queue or list backed by a growable circular array.
* efficient queue or list backed by a growable circular array.
* <p/> * <p/>
* Unlike {@link java.util.concurrent.ArrayBlockingQueue}, this class is * Unlike {@link java.util.concurrent.ArrayBlockingQueue}, this class is able to grow and provides a blocking put call.
* able to grow and provides a blocking put call.
* <p/> * <p/>
* The queue has both a capacity (the size of the array currently allocated) * The queue has both a capacity (the size of the array currently allocated) and a max capacity (the maximum size that may be allocated), which defaults to
* and a max capacity (the maximum size that may be allocated), which defaults to
* {@link Integer#MAX_VALUE}. * {@link Integer#MAX_VALUE}.
* *
* @param <E> The element type * @param <E>
* The element type
*/ */
public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQueue<E> public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQueue<E>
{ {
/** /**
* The head offset in the {@link #_indexes} array, displaced * The head offset in the {@link #_indexes} array, displaced by 15 slots to avoid false sharing with the array length (stored before the first element of
* by 15 slots to avoid false sharing with the array length * the array itself).
* (stored before the first element of the array itself).
*/ */
private static final int HEAD_OFFSET = MemoryUtils.getIntegersPerCacheLine() - 1; private static final int HEAD_OFFSET = MemoryUtils.getIntegersPerCacheLine() - 1;
/** /**
* The tail offset in the {@link #_indexes} array, displaced * The tail offset in the {@link #_indexes} array, displaced by 16 slots from the head to avoid false sharing with it.
* by 16 slots from the head to avoid false sharing with it.
*/ */
private static final int TAIL_OFFSET = HEAD_OFFSET + MemoryUtils.getIntegersPerCacheLine(); private static final int TAIL_OFFSET = HEAD_OFFSET + MemoryUtils.getIntegersPerCacheLine();
/** /**
@ -82,7 +78,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
/** /**
* Creates an unbounded {@link BlockingArrayQueue} with default initial capacity and grow factor. * Creates an unbounded {@link BlockingArrayQueue} with default initial capacity and grow factor.
* *
* @see #DEFAULT_CAPACITY * @see #DEFAULT_CAPACITY
* @see #DEFAULT_GROWTH * @see #DEFAULT_GROWTH
*/ */
@ -94,10 +90,10 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/** /**
* Creates a bounded {@link BlockingArrayQueue} that does not grow. * Creates a bounded {@link BlockingArrayQueue} that does not grow. The capacity of the queue is fixed and equal to the given parameter.
* The capacity of the queue is fixed and equal to the given parameter. *
* * @param maxCapacity
* @param maxCapacity the maximum capacity * the maximum capacity
*/ */
public BlockingArrayQueue(int maxCapacity) public BlockingArrayQueue(int maxCapacity)
{ {
@ -108,9 +104,11 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
/** /**
* Creates an unbounded {@link BlockingArrayQueue} that grows by the given parameter. * Creates an unbounded {@link BlockingArrayQueue} that grows by the given parameter.
* *
* @param capacity the initial capacity * @param capacity
* @param growBy the growth factor * the initial capacity
* @param growBy
* the growth factor
*/ */
public BlockingArrayQueue(int capacity, int growBy) public BlockingArrayQueue(int capacity, int growBy)
{ {
@ -121,10 +119,13 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
/** /**
* Create a bounded {@link BlockingArrayQueue} that grows by the given parameter. * Create a bounded {@link BlockingArrayQueue} that grows by the given parameter.
* *
* @param capacity the initial capacity * @param capacity
* @param growBy the growth factor * the initial capacity
* @param maxCapacity the maximum capacity * @param growBy
* the growth factor
* @param maxCapacity
* the maximum capacity
*/ */
public BlockingArrayQueue(int capacity, int growBy, int maxCapacity) public BlockingArrayQueue(int capacity, int growBy, int maxCapacity)
{ {
@ -136,18 +137,18 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* Collection methods */ /* Collection methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
@Override @Override
public void clear() public void clear()
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
_indexes[HEAD_OFFSET] = 0; _indexes[HEAD_OFFSET] = 0;
@ -156,12 +157,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@ -178,7 +179,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* Queue methods */ /* Queue methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
@SuppressWarnings("unchecked") @SuppressWarnings("unchecked")
@ -189,8 +190,8 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
return null; return null;
E e = null; E e = null;
final Lock headLock = _headLock;
headLock.lock(); // Size cannot shrink _headLock.lock(); // Size cannot shrink
try try
{ {
if (_size.get() > 0) if (_size.get() > 0)
@ -205,7 +206,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
return e; return e;
} }
@ -218,8 +219,8 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
return null; return null;
E e = null; E e = null;
final Lock headLock = _headLock;
headLock.lock(); // Size cannot shrink _headLock.lock(); // Size cannot shrink
try try
{ {
if (_size.get() > 0) if (_size.get() > 0)
@ -227,7 +228,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
return e; return e;
} }
@ -251,7 +252,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* BlockingQueue methods */ /* BlockingQueue methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
@Override @Override
@ -259,10 +260,8 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
{ {
Objects.requireNonNull(e); Objects.requireNonNull(e);
final Lock tailLock = _tailLock;
final Lock headLock = _headLock;
boolean notEmpty = false; boolean notEmpty = false;
tailLock.lock(); // Size cannot grow... only shrink _tailLock.lock(); // Size cannot grow... only shrink
try try
{ {
int size = _size.get(); int size = _size.get();
@ -272,7 +271,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
// Should we expand array? // Should we expand array?
if (size == _elements.length) if (size == _elements.length)
{ {
headLock.lock(); _headLock.lock();
try try
{ {
if (!grow()) if (!grow())
@ -280,7 +279,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
@ -292,19 +291,19 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
if (notEmpty) if (notEmpty)
{ {
headLock.lock(); _headLock.lock();
try try
{ {
_notEmpty.signal(); _notEmpty.signal();
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
@ -339,8 +338,8 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
public E take() throws InterruptedException public E take() throws InterruptedException
{ {
E e = null; E e = null;
final Lock headLock = _headLock;
headLock.lockInterruptibly(); // Size cannot shrink _headLock.lockInterruptibly(); // Size cannot shrink
try try
{ {
try try
@ -366,7 +365,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
return e; return e;
} }
@ -377,8 +376,8 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
{ {
long nanos = unit.toNanos(time); long nanos = unit.toNanos(time);
E e = null; E e = null;
final Lock headLock = _headLock;
headLock.lockInterruptibly(); // Size cannot shrink _headLock.lockInterruptibly(); // Size cannot shrink
try try
{ {
try try
@ -406,7 +405,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
return e; return e;
} }
@ -414,12 +413,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
@Override @Override
public boolean remove(Object o) public boolean remove(Object o)
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
if (isEmpty()) if (isEmpty())
@ -432,9 +431,9 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
int i = head; int i = head;
while (true) while (true)
{ {
if (Objects.equals(_elements[i], o)) if (Objects.equals(_elements[i],o))
{ {
remove(i >= head ? i - head : capacity - head + i); remove(i >= head?i - head:capacity - head + i);
return true; return true;
} }
++i; ++i;
@ -446,36 +445,36 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@Override @Override
public int remainingCapacity() public int remainingCapacity()
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
return getCapacity() - size(); return getCapacity() - size();
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@ -492,19 +491,19 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* List methods */ /* List methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
@SuppressWarnings("unchecked") @SuppressWarnings("unchecked")
@Override @Override
public E get(int index) public E get(int index)
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
if (index < 0 || index >= _size.get()) if (index < 0 || index >= _size.get())
@ -517,12 +516,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@ -532,12 +531,11 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
if (e == null) if (e == null)
throw new NullPointerException(); throw new NullPointerException();
final Lock tailLock = _tailLock; _tailLock.lock();
tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
final int size = _size.get(); final int size = _size.get();
@ -568,30 +566,30 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
if (i < tail) if (i < tail)
{ {
System.arraycopy(_elements, i, _elements, i + 1, tail - i); System.arraycopy(_elements,i,_elements,i + 1,tail - i);
_elements[i] = e; _elements[i] = e;
} }
else else
{ {
if (tail > 0) if (tail > 0)
{ {
System.arraycopy(_elements, 0, _elements, 1, tail); System.arraycopy(_elements,0,_elements,1,tail);
_elements[0] = _elements[capacity - 1]; _elements[0] = _elements[capacity - 1];
} }
System.arraycopy(_elements, i, _elements, i + 1, capacity - i - 1); System.arraycopy(_elements,i,_elements,i + 1,capacity - i - 1);
_elements[i] = e; _elements[i] = e;
} }
} }
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@ -601,12 +599,11 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
{ {
Objects.requireNonNull(e); Objects.requireNonNull(e);
final Lock tailLock = _tailLock; _tailLock.lock();
tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
if (index < 0 || index >= _size.get()) if (index < 0 || index >= _size.get())
@ -622,12 +619,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@ -635,12 +632,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
@Override @Override
public E remove(int index) public E remove(int index)
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
if (index < 0 || index >= _size.get()) if (index < 0 || index >= _size.get())
@ -655,16 +652,16 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
int tail = _indexes[TAIL_OFFSET]; int tail = _indexes[TAIL_OFFSET];
if (i < tail) if (i < tail)
{ {
System.arraycopy(_elements, i + 1, _elements, i, tail - i); System.arraycopy(_elements,i + 1,_elements,i,tail - i);
--_indexes[TAIL_OFFSET]; --_indexes[TAIL_OFFSET];
} }
else else
{ {
System.arraycopy(_elements, i + 1, _elements, i, capacity - i - 1); System.arraycopy(_elements,i + 1,_elements,i,capacity - i - 1);
_elements[capacity - 1] = _elements[0]; _elements[capacity - 1] = _elements[0];
if (tail > 0) if (tail > 0)
{ {
System.arraycopy(_elements, 1, _elements, 0, tail); System.arraycopy(_elements,1,_elements,0,tail);
--_indexes[TAIL_OFFSET]; --_indexes[TAIL_OFFSET];
} }
else else
@ -680,24 +677,24 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
@Override @Override
public ListIterator<E> listIterator(int index) public ListIterator<E> listIterator(int index)
{ {
final Lock tailLock = _tailLock;
tailLock.lock(); _tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
Object[] elements = new Object[size()]; Object[] elements = new Object[size()];
@ -707,30 +704,30 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
int tail = _indexes[TAIL_OFFSET]; int tail = _indexes[TAIL_OFFSET];
if (head < tail) if (head < tail)
{ {
System.arraycopy(_elements, head, elements, 0, tail - head); System.arraycopy(_elements,head,elements,0,tail - head);
} }
else else
{ {
int chunk = _elements.length - head; int chunk = _elements.length - head;
System.arraycopy(_elements, head, elements, 0, chunk); System.arraycopy(_elements,head,elements,0,chunk);
System.arraycopy(_elements, 0, elements, chunk, tail); System.arraycopy(_elements,0,elements,chunk,tail);
} }
} }
return new Itr(elements, index); return new Itr(elements,index);
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* Additional methods */ /* Additional methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/** /**
@ -738,7 +735,15 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
*/ */
public int getCapacity() public int getCapacity()
{ {
return _elements.length; _tailLock.lock();
try
{
return _elements.length;
}
finally
{
_tailLock.unlock();
}
} }
/** /**
@ -750,7 +755,7 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
/* Implementation methods */ /* Implementation methods */
/*----------------------------------------------------------------------------*/ /*----------------------------------------------------------------------------*/
private boolean grow() private boolean grow()
@ -758,12 +763,11 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
if (_growCapacity <= 0) if (_growCapacity <= 0)
return false; return false;
final Lock tailLock = _tailLock; _tailLock.lock();
tailLock.lock();
try try
{ {
final Lock headLock = _headLock;
headLock.lock(); _headLock.lock();
try try
{ {
final int head = _indexes[HEAD_OFFSET]; final int head = _indexes[HEAD_OFFSET];
@ -776,14 +780,14 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
if (head < tail) if (head < tail)
{ {
newTail = tail - head; newTail = tail - head;
System.arraycopy(_elements, head, elements, 0, newTail); System.arraycopy(_elements,head,elements,0,newTail);
} }
else if (head > tail || _size.get() > 0) else if (head > tail || _size.get() > 0)
{ {
newTail = capacity + tail - head; newTail = capacity + tail - head;
int cut = capacity - head; int cut = capacity - head;
System.arraycopy(_elements, head, elements, 0, cut); System.arraycopy(_elements,head,elements,0,cut);
System.arraycopy(_elements, 0, elements, cut, tail); System.arraycopy(_elements,0,elements,cut,tail);
} }
else else
{ {
@ -797,12 +801,12 @@ public class BlockingArrayQueue<E> extends AbstractList<E> implements BlockingQu
} }
finally finally
{ {
headLock.unlock(); _headLock.unlock();
} }
} }
finally finally
{ {
tailLock.unlock(); _tailLock.unlock();
} }
} }